On 11/30/2020 10:51 AM, Stephen Gaito wrote:
Hello,
I am slowly working on a Mathematical problem requiring underlying
computation.
As Mathematicians (myself included) are rather "conservative", I need
to discuss each "chunk" of code with the full set of Mathematical
notation.
A couple of years ago I started using ConTeXt-MKIV as a
Mathematically-Literate-Programming tool by using its excellent Lua
interface to capture the code and dump it to disk for external
compilation.
I am now revisiting my original design and want to redo my tools using
ConTeXt-LMTX.
I would *like* to be able to "stop" the ConTeXt typesetting at various
points for differing purposes:
1. After all macro expansions (and hence after *my* calls into Lua)
but before line/paragraph/page layout begins.
maybe something
\startmystuff
\stopmystuff
and then you can hook something into startmystuff and \stopmystuff
2. After line/paragraph/page layout but before PDF generation.
pdf is generated per page, if needed one can kick in a shipout overload
but keep in mind that multipass data is flushed as part of the shipout
(because it is often location and order bound)
3. After all PDF generated (ie. a "normal" "full" ConTeXt run).
Stopping after all macro expansions would allow my code generation
builds to proceed without the un-needed page setting or PDF generation.
hm, the problem is always in the 'state' of all kind of variables
Stopping after the line/paragraph/page layout would allow multiple
"faster(?)" ConTeXt runs while the "*.tuc" file converges to a complete
set of page numbers and cross references (etc). Then, once the "*.tuc"
file has converged, a full ConTeXt run with PDF output could be
done.
not sure what you mean here ... what is fast? or: how slow is it now?
what is the bottleneck? can you cache data that didn't change?
a large document is normally split up in sections that can be processed
independent
\starttext
\dorecurse{10000}{\samplefile{ward}\par}
\stoptext
runs on my 2013 laptop at over 65 pages per second
quite often performance is hit by inefficient styling and such .. it's
no problem to bring a tex system a grinding halt
I am very aware that *internally* ConTeXt is probably structured as a
tight pipeline with each of the "traditional" TeX stages "Mouth",
"Stomach", "page setting", PDF generation.... tightly "chained"...
This means that there is no "one" place in the code where all macro
expansions have completed but before the page setting "starts", or
similarly, after the page setting has finished but before the PDF
generation "starts".
yes and often something is left over for a next page so it's kind of fluid
----
QUESTION: Is it possible to use the new LuaMetaTeX callbacks (found in
chapter 10 of the "LuaMetaTEX Reference Manual") to "suppress" any
further computation at various points in the ConTeXt pipeline?
----
sure, you can kick in handlers at various stages (assuming that you keep
in mind where you kick them in as there is some order involved)
For example, could I use one of the "*_linebreak_filter"s (or the
"append_to_vlist_filter") to "return" an empty value and hence reduce
further computation downstream in the pipeline?
you can but linebreak is not the most costly one, you probbaly want to
intercept the list builder but when you do that you can as well do a
\stoptext which prevents further reading of content (but i probably
misunderstand)
Could I use the "pre_output_filter" to "return" an empty value and
hence "stop" PDF generation?
assuming a properky structured document forcing a \stoptext should work
in most cases
(I realize that these callbacks *are* a currently fast moving target. I
am happy to follow their changes, equally I would be testing their
usefulness and/or impact)
actually, the callbacks themselves hardly change, but the code plugged
into them might occasionally (a lot of mkiv code is already quite old so
i'm now looking at it and see if i can use some recent tricks)
ALTERNATIVE QUESTION: Would it be possible to provide official
ConTeXt-LMTX "modes" which suppress further computation at these points?
the question is: what do you want to suppress? best first identify the
bottleneck and then figure out what can be skipped (as mentioned:
multipass data can be made more independent I guess but it still demands
some calculations and analyzing and it's that bit that takes the time)
This alternative, while some more work for the writing of
ConTeXt-LMTX, would ensure less direct external dependence on the
LuaMetaTeX callbacks, but would almost certainly be welcomed by the
ConTeXt community.
i need more info (also from others then) about what the reason, goal and
possible gain is
- tex: the context code is quite efficient, and tex is quite fast, so
there's little to gain there (but as said one can write slow macros that
spoil that game)
- lua: on the average lua is fast but garbage collection can be of
influence (i need to see code in order to be able to tell if there is a
gain there); the lua code in context is quite ok but for instance
messing with node lists will always come at a cost (crossing the c
boundary and such)
- pdf: the backend code in luametatex is somewhat slower than in luatex
but we're gaining there (because in related areas we can do things
different, although there is new functionality that when used also comes
at a price); but as far as i can tell a luametatex run here is on the
average some 20% faster than a luatex run so the pdf generation slowdown
gets kind of obscured by it
----
QUESTION: Are the "stages" I have identified major, computationally
expensive, "steps" in the overall ConTeXt "computation"?
----
basic typesetting (hyphenation, font handling): takes a bit of time,
extra features that you use add some too: some timings are reported
after a run so you get an idea
par building: unles hz is used, quite fast
page building: fast but depending on what features are enables
finalizing the page can take some time
expansion: pretty fast on the average
summary: try to identify where the bottlenecks are
you can run with
\enabletrackers[pages.timing]
(put it on cont-loc.mkxl somewhere in in texmf-local) and get timings
per page (i have that enabled on my machine)
Hans
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